1. Technical Field of the Invention
The present invention relates to a mobile communication service, and more particularly to a method for providing a closed user group service capable of transmitting a particular message to mobile stations(terminals) belonging to a certain group in a mobile communication network.
2. Description of the Prior Art
FIG. 1 shows a block diagram illustrating a mobile communication network employed in the general cell broadcast service.
The reference numeral 101 denotes a cell broadcast center/short message center(CBC/SMC), 102 an information provider(IP), 103 a mobile communication network such as a cellular or personal communication service(PCS) network, 104 a mobile telephone, and 105 an exclusive terminal for cell broadcast such as a notebook computer (a lap top computer) or a palm top computer.
The CBC/SMC 101 receives cell broadcast messages from the information provider 102, performs cell broadcast scheduling and processes for respectively writing special message identifiers to storage devices of the mobile stations 104 and 105 using teleservice identifiers(TI), selects a base station controller/base station transceiver system(BSC/BTS) to which the messages are transmitted and then decides interface between the CBC/SMC 101 and the mobile communication network 103.
The information provider 102, which is one of a plurality of information sources, provides information to be cell broadcasted.
The mobile communication network 103 performs processes for transmitting the cell broadcast messages from the CBC/SMC 101 to each of terminals in the cell.
It should be possible for the mobile stations 104 and 105 to receive the cell broadcast messages and to display the receipt of the messages. The mobile station 104 may be an audio terminal with display function of the received message such as a mobile telephone. The mobile station 105 may be an exclusive terminal such as a notebook computer and a palm top computer. Each of mobile stations 104 and 105 compares the message identifier of the received messages with that saved on its own internal storage device. Then, the mobile stations 104 and 105 display the received messages, if the message identifier of the received messages is equal to the message identifier saved on its own internal storage device.
The cell broadcast service is an one-way service in which the CBC/SMC transmits particular messages to all the mobile terminals within a selected area(which is referred to as `cell`). In other words, the CBC/SMC receives various kinds of information from the information providers 102 and transmits the information to a plurality of users such as a mobile telephone 104 or an exclusive terminal 105. The plurality of the users can be simultaneously receive the information. The information may include a weather forecasting, information about stock exchange, information about sports, traffic information, discharge rate of charge, and etc.
The closed user group service(CUG) is a service which provides only users belonging to a particular group with special cell broadcast messages.
Let's assume that there are three groups A, B and C in the same cell, and that the CBC/SMC wants to make the users belonging to the group "A" come back to their office. In the prior cell broadcast service, if the CBC/SMC transmits the message "Please quickly return to the office.", all of users in the cell receive the message. The users belonging to the groups B and C are confused of the message. On the other hands, if the CBC/SMC transmits message "Men and women belonging to the group A, please quickly return to the office.", the users belonging to the groups B and C receive the unnecessary message even if there is no confusion.
Therefore, there is a need for a method for making only users belonging to a particular group receive a certain message in spite of using the prior cell broadcast service network.